Nuclear medicine is a unique medical specialty wherein radiation is used to acquire images which show the function and anatomy of organs, bones or tissues of the body. Radiopharmaceuticals are introduced into the body, either by injection or ingestion, and are attracted to specific organs, bones or tissues of interest. Such radiopharmaceuticals produce gamma photon emissions which emanate from the body. One or more detectors are used to detect the emitted gamma photons, and the information collected from the detectors is processed to calculate the position of origin of the emitted photon from the source (i.e., the body organ or tissue under study). The accumulation of a large number of detected gamma positions allows an image of the organ or tissue under study to be displayed.
In certain nuclear tomographic imaging techniques, such as Single Photon Emission Computed Tomography (SPECT), events are detected by one or more collimated radiation detectors, also referred to as gamma cameras, which are typically rotated about a patient's body in a defined orbital path. The collimators employed with such detectors have apertures running through the body of the collimator to assure that only gamma photons traveling along specific paths aligned with the holes will pass through to the detector. Upon detection of a gamma ray, it is inferred that the gamma ray then came along the same path that the collimator hole is directed.
It should be appreciated that the length, septa thickness, and dimensions of the holes in the collimator affect the resolution and sensitivity of the gamma detector.
In the past, collimator design has been non-adaptive, meaning that the length, septa and dimensions of the collimator holes could not be adjusted. If different resolution and sensitivity is desired, the collimator would have to be replaced with another having different dimensions and characteristics. Such non-adaptive collimators can be illustrated in FIG. 1.
In the non-adaptive collimator displayed in FIG. 1, L is the length of the collimator 1, t is the thickness of the septum, HD is the hole diameter, and R is the distance from the collimator face to the radiation source 2. As illustrated, length L would remain constant and unvarying in conventional collimators. Resolution can be defined as follows:
      R    c    =            HD      L        ⁢          (              R        +        L            )      where HD, L, and R are defined as above and Rc is resolution. The length, hole diameter and distance to the radiation source (in a typical fixed-gantry camera) are not adjustable; therefore the resolution cannot be varied. (It is noted that even the distance R from the face of the collimator to the radiation source were to be varied, the effect on resolution is minimal because of the typical values of R and L involved.)
What is needed is an apparatus or method which enables variation of the collimator characteristics to enable resolution to be adjusted.